平衡放大器

Balanced AmplifiersSheet 1 of 14

Balanced Amplifiers The single amplifier meets the specification for noise figure and again but fails to meet the return loss specification due to the large mis-matches on the input & outputs. To overcome this problem one solution is to use a balanced amplifier topography, which is shown in Figure 1.

NOTE Dashed lines are reflected signals

Figure 1 Schematic diagram of a balanced amplifier using two quadrature hybrids (eg Lange Couplers). The balanced amplifier employs two quadrature hybrids in this case two lange couplers (although branchline couplers can be used). Any reflections of an incident signal on the input due to the poor match of the amplifiers will be channelled back through the input lange to the 50 ohm load where they will be absorbed,and similarily on the th